Process for crimping polyester filament yarn

ABSTRACT

Textile filaments which have asymmetric shrinkage properties, and may be heat-relaxed to provide a high crimp frequency and a narrow crimp frequency distribution, are produced by meltspinning a single synthetic linear polymer composition, drawing the filaments and then passing them over an unheated wearresistant pin at high speed. The process condition are controlled to provide filaments of regular cross-sectional configuration having a modified minor portion, distinguishable from the remainder of the filament by a different refractive index, which extends substantially continuously along the filament.

nited States Patent Frankfort et a1.

[ 1*Sept. 16, 1975 PROCESS FOR CRIIVIPING POLYESTER FILAMENT YARN Inventors: Hans R. E. Frankfort, Kinston,

Assignee:

Notice:

Filed:

3,816,992, which is a continuation-in-part of Ser. No. 210,884, Dec. 22, 1971, abandoned.

US. Cl. 28/72.l7; 57/140 Del.

Peter F. Lyons, Wilmington,'

E. I. Du Pont de Nemours and Company, Wilmington, Del.

The portion of the term of this patent subsequent to June 18, 1991, has been disclaimed.

May 31, 1974 Appl. No.: 476,129

Related US. Application Data Continuation-impart of Ser. Nos. 281,972, Aug. 18, 1972, and Ser. No. 353,808, April 23, 1973, Pat. No.

Int. Cl. D02J l/22; DO2G 1/16 Field of Search 28/72.l2, 72.13, 72.17,

140 BY, 140 J, 157 R, 157 F, 157 MS, 34 R, 34 D [56] References Cited UNITED STATES PATENTS 2,974,391 3/1961 Speakman et a1. 28/72.l3 X 3,115,744 12/1963 Nott 28/72.17 X 3,226,792 1/1966 Starkie 28/72.l7 X 3,317,978 5/1967 McIntosh et a1 28/72.l7 X 3,358,345 12/1967 Daniel 28/1.2

3,379,809 4/1968 Woods 264/168 3,816,992 6/1974 Frankfort et a1 28/72. 17 X Primary Examiner-Louis K. Rimrodt [57] ABSTRACT 21 Claims, 3 Drawing Figures 1 FOR CRIMPING POLYESTER- FILAMENT YARN REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION The present invention is concerned with production of polyester and polyamide filaments'which crimp due to asymmetric shrinkage when relaxed.

Filaments which crimp due to asymmetric shrinkage when relaxed have been prepared by a variety of methods. Kilian U.S. Pat. No. 3,050,82l discloses polyester filaments which have been asymmetrically quenched during melt spinning, by blowing cooling air against one side of the filaments as they emerge from the spin neret. When drawn and then relaxed, the filaments will shrink to a greater extent on one side of the filament, but a relatively low crimp frequency is obtained in this manner.

Crimpability has been imparted by passing filaments over a sharp edge. This weakens the filament and improvements in the crimp obtained are desirable. The edge-treated side is on the inside of crimp bends. Terumichi Ono et al. U.S. Pat. No. 3,600,271 discloses that a better crimped product is obtained when previously undrawn 6-nylon is drawn over a cylindrical pin heated to about 600C. However, Yukio Mitsuishi et al. U.S. Pat. No. 3,538,566 teaches that milder conditions must be used for polyester filaments. Lower pin temperatures are used and the filaments are wet when drawn over the pin in theprocess of this patent. The results obtainedat various pin temperatures and filament speeds of 200 to 600 meters per minute indicate that undesirably low crimp frequencies are obtained.

Edington et al. U.S. Pat. No. 3,224,068 discloses a process in which the treatment is performed after the filaments havebeen drawn, so that higher temperatures can be used. As illustrated, polyester filaments are passed at speeds of up to 450 yards per minute over a strip of tungsten or tungsten carbide which is about 0.030 inch wide and heated to 365C-375C. Special heating means are used to maintain the strip at an even temperature. The relaxed product is said to have a broad range of crimp amplitudes and crimp frequencies along the filament length, and sections with no crimp at all, but to be an improvement over previous products obtained by treatment with the usual electrically heated wire, pin or bar.

Potman et al. U.S. Pat. No. 3,601,872 discloses that 6-nylon carpet yarn of increased voluminosity can be prepared by introducing two crimps separately into a yarn, a latent crimp by asymmetric treatment with a heated pin and a direct crimp by subjecting the yarn to direct crimping treatment by a gear-crimping, a stufferbox crimping, or an air-crimping treatment.

SUMMARY OF-THE INVENTION The present. invention provides for production of multifilament yarns of filaments which, in the heatrelaxed form, have an especially desirable crimp frequency distribution. Additional advantages of the in- PROCESS 2 vention will become apparent from the specification and drawings.

The invention is an improvement over previous processes for preparing crimpable yarns by passing a yarn bundle of filaments, spun from a single synthetic linear organic thermoplastic polymer, in contact with a heated surface to provide asymmetric shrinkage properties on opposite sides of filaments. The improvement of the present invention comprises (a) drawing the filaments to provide the approximate break elongation desired in the product and (b) passing the drawn filaments at high speed in frictional contact with a durable, wear-resistant surface under frictional tension sufficient to generate all of the heat required to provide the desired asymmetric shrinkage properties without otherwise heating the wear-resistant surface.

The drawn filaments should be passed in frictional contact with the durable, wear-resistant surface at a speed of at least 900 yards per minute, and more preferably at a speed of at least 2,000 yards per minute. There appears to be no upper limit to thespeeds which can be used but speeds within the range of 1,000 to 4,500 yards per minute are generally used.

The yarn filaments must be drawn before the filaments contact the wear-resistant surface in step (b). The drawn filaments preferably have a break elongation of less than 40 percent. Preferably they are drawn so as to have 5 to 25 percent boil-off shrinkage. A preferred process is a coupled spin/draw/pin-texturing process in which the yarn is drawn to have 15 to 40 percent break elongation and 8 to 16 percent boil-off shrinkage prior to contact, in step (b), with a pin having a durable, wear-resistant surface. The temperature of the yarn just prior to the wear-resistant surface should be from 25 to C., although higher temperatures may be used.

The filaments must contact the wear-resistant surface under a frictional tension sufficient to generate all of the heat required to provide the desired asymmetric shrinkage properties without otherwise heating the wear-resistant surface. The term frictional tension is used herein to designate the tension on the filaments immediately after the surface minus the tension on the filaments immediately before the surface. Generally, this value is 0.7 m7 grams per filament; preferably the tension difference is l to 2 g./fil. for polyesters and 4 to 5 g./fil. for polyamides.

The filaments usually make frictional contact with the wear-resistant surface for a distance of 0.5 to 15 millimeters. Preferably, the process is operated so that the filaments are in contact with the surface for a distance of l to 10 millimeters. Preferably, the durable, wear-resistant surface is provided by a cylindrical pin 3 to 10 millimeters in diameter, but the contact surface can be provided by other means known to the art. The filaments usually contact the surface of the cylindrical pin over an arc of 30 to and preferably between 45 and 90.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of process and apparatus suitable for continuously melt-spinning drawing and treating filaments in accordance with the invention.

FIG. 2 is a schematic representation of process and apparatus for treating previously drawn yarn in accordance with the invention.

In practicing the present invention, the filaments may consist of any single composition of linear organic thermoplastic polymer conventionally used for textile filaments and yarns. The single composition may comprise intimate mixtures of polymers and/or copolymers and may contain minor amounts of other additives, such as delusterants, antistatic agents, or other monomeric or polymeric additives. Polyesters and polyamides are preferred polymers. An especially preferred polyester is polyethylene terephthalate (ZGT), as homopolymer or copolymerized with minor amounts of other components. Such copolymerized polyesters include poly- (ethylene terephthalate/isophthalate poly(ethylene terephthalate/adipate) and poly (ethylene terephthalate/'(sodium sulfo )-isophthalate). Other polyesters include poly(tetramethylene terephthalate) and poly (l,4-cyclohexylenedimethylene terephthalate). Among the polyamide polymers that are preferred are hexamethylene adipamide (nylon 6-6) and the polyamide obtained from bis-(para-aminocyclohexyl) methane and dodecane dioic acid.

The process of the present invention requires that the filaments must be drawn before being treated asymmetrically. Sufficient drawing is necessary to assure that adequatetension conditions can be maintained when the filaments are subsequently passed in frictional contact with the wear-resistant surface. Preferably the drawing is conducted so that the drawn filaments have the approximate break elongation and boil-off shrinkage desired in the product. Usually, it is desired that the break elongation be between 15 and 40 percent, preferably 25 to 35 percent and the boil-off shrinkage be between 5 and 25 percent, preferably 8 to 16 percent.

In the asymmetric treatment step following drawing, the filaments are passed at high speed in frictional contact with a durable, wear-resistant surface. The temperature of the filaments fed to the surface is generally between 25 and l 10C., although higher temperatures may be used. Care should be taken that each filament contacts the surface in approximately the same manner. Preferbly, the bundle of filaments is not twisted and the filaments pass over the surface as a single layer of individual filaments. The frictional contact of the filaments with the surface is sufficient to generate enough heat to asymmetrically modify the shrinkage properties of the filaments. No other heating of the wear-resistant surface is necessary.

High speeds are required in the present invention for passing the filaments in frictional contact with the otherwise unheated wear-resistant surface in order to achieve satisfactory asymmetric shrinkage properties in the final product. Usually, filament speeds of at least 900 yards per minute (l,370 cm/sec) are satisfactory, but speeds of at least 2,000 yards per minute (3,050 cm/sec) are preferred. There appears to be no upper limit to the speeds which can be used, but speeds within the range of 1,000 to 4,500 yards per minute 1,525 to 6,860 cm/sec) are generally used.

The tension on the filaments, during passage in frictional contact with the wear-resistant surface, undergoes a distinct change due to the frictional work that is done. This change in tension is equal to tension on the filaments immediately after passage over the surface 4 minus the tensionimmediately before passage over the surface. Tension differences of 0.7 to 7 grams per filament are useful, with 1 to 2 g./fil. for polyesters and 4 to 5 g./fil. for polyamides being preferred. These tension differences generally apply to filaments of about 1.5 to 10 denier.

During operation of the process, the filaments usually make frictional contact with the wear-resistant surface for a distance of 0.5 to 15 millimeters, and preferably contact the surface for a distance of l to 10 millimeters. Usually the wear-resistant surface is a curved surface, most conveniently provided by a cylindrical pin. Pin diameters of about 1 to 15 millimeters are suitable; 3,to 10 millimeters, are preferred. When a cylindrical pin is used, the are over which the filaments usually contact the pin surface is between 30 to 180, and preferably between 45 and Durable, wear-resistant surfaces are needed for satisfactory long-term continuous operation. Ceramic pins of the type commonly used for guides and draw pins in textile processes are suitable. The use of Alsimag, glass and stainless steel pins is illustrated in the Examples. Other metals with durable surfaces are also satisfactory.

To impart asymmetric shrinkage characteristics to any conventional textile filament of synthetic linear organic thermoplastic polymer by means of the process of the present invention, the variables discussed above preferably are adjusted so that the value of AT max calculated by the following formula is at least C. and usually below 300C:

' V A T max 0.0283 (f f,) Um! length between the filaments and the surface in cm.; k

is the thermal conductivity of the filaments in cal./cm- .sec.C.; c is the specific heat of the filaments in cal./g.C.; and d is the denier per filament. The AT max parameter is related to the asymmetric temperature distribution that is imposed' on the filament by the frictional heat generation and is referred to herein as the temperature rise parameter.

For conventional polyester textile filaments, the above formula simplifies to the following:

For conventional polyamide textile filaments, formula (l simplifies to the following:

ATmax= 1.92 (f -f Especially preferred operating conditions are obtained in the practice of the present invention when AT max values of at least C. are used with polyester filaments and of at least 200C. are used with polyamide filaments.

A continuous process for preparing asymmetrically treated filaments in accordance with the present invention is shown in FIG. 1. Filaments are melt-spun from spinneret 11 and allowed to cool as they descend from the spinneret. The filaments then converge and which have a considerably higher surface speed than I the feed rolls to draw the yarn. A traversing mechanism 16 is provided for guiding the filaments onto the draw rolls. When activated, the mechanism 16 varies the.

path of the drawn filaments on the rolls and over a wear-resistant pin 17, which is referred to herein as a texturing pin. It is at pin. 17 that the asymmetric treatment of the filaments occurs. The drawn filaments pass over texturing pin 17 witha change of direction 6,-

and pass around pulling rolls 18 which provide tension over the texturing pin 17. If desired, the filaments can be guided to the texturing pin by an adjustable idler roll I (not shown) to facilitate changing the wrap angle 0 at I the texturing pin in order to increase or decrease the length of pin-filament contact. The filaments pass from the pulling rolls 18 over a postdraw finish roll 19 to wind-up 20, which cross-winds the product under a tension that is best measured shortly after the postdraw finish roll.

In operating the process of the present invention, normal levels of finish, such as are typically used in spinning-drawing-winding operations, are used. Excess finish should be avoided so as not to have it interfere with frictional work at the pin-filament contact site.

Crimp is developed in the above product by a subsequent heat relaxation treatment. However, the processes may be combined to produce a crimped product in one continuous operation. lnsteadof wind-up 20, the filaments may be passed through heating means on a conveyor in relaxed condition and then cooled prior to being wound up. On the other hand, the melt-spinning, drawing and pin-texturing sequence can be split in various ways. The melt-spinning can be a separate operation. A conventional melt-spinning and drawing process can be used to produce yarn which is later pin-textured in a separate operation.

FIG. 2 illustrates such a separate operation wherein untwisted, drawn and packaged yarn is fed over-end to the pin-texturing treatment. The yarn passes from package 21 through tension gate 22- and over roller 23 to a pair of feed rolls 24. The yarn makes several wraps about the pair of feed rolls, proceeds to a pair of stretch rolls 25, makes several wraps about the pair of stretch rolls, passes over texturing pin 26 at a wrap angle 0, and proceeds over roller 27 to wind-up 28. The yarn passing over the texturing pin may be an inner wrap, i.e., the yarn passes from the pin back to the stretch rolls. Alternatively, the yarn may pass from the pin to separate pulling rolls without returning to'the stretch rolls".

In the pin-texturing portion of the above-described processes, wherein the filaments are-fed to they frictional contact surface (e.g., a pin) by feed rollsand withdrawn therefrom by takeup rolls, the filaments usu' ally are stretched by no more than 10 percent and preferably by no more than 5 percent. When operating the invention with a process in which the melt spinning and drawing are separated fromthe pin-texturing step, a stretch of substantially zero=:(i-.e.", no stretchinglican be used satisfactorily in the pin-texturing 'step. With 6 polyester yarns in a continuous process, it is preferred to operate with a stretch of between 2 and 5 percent.

The multifilament yarns produced in accordance withithe above-described processes of the invention may be of any conventional denier/filament count. Generally, yarns of about 35 to 250 denier having 10 to 200 filaments are suitable. Yarns having 17 to 50 filaments are..preferred. Yarn counts of /34 to 190/34 are especially preferred. Filament deniers of l.510 are suitable, but 2-5 are preferred.

Crimp may be developed in the yarns produced according to the invention by any of the many wellknown conventional heat-relaxation treatments. In general, these treatments allow the yarn to shrink freely while exposed to hot water, steam or dry heat. In the I method used herein for comparing the crimp frequencies of filaments, the filaments are suspended free of tension in an oven through which hot air at 180C. is gently circulated for five minutes and then the filaments are allowed to cool while still free from tension. Filaments which have been relaxed by other methods are. also retreated by this test method to standardize crimp measurements.

The process of the present invention also provides a particularly useful, novel polyester filament which when heat-relaxed has an especially desireable crimp frequency distribution. Yarns made of such filaments have additional advantages in use, which will be discussed below. This product of the invention is a textile filament having asymmetric properties and an abraded surfaceextending along one side of the filament, and consisting of a single synthetic linear polyester composition: The filament has a modified minor portion'distinguishable by a difference in refractive index, which extends substantially continously along the abraded side of the filament. The continuity of this minor portion is such that less than 5 percent, preferably less than 3 percent, of the filament length is occupied by discontinuities longer than millimeters and the average length of all discontinuities is less than 2 millimeters, preferably less than 1.5 mm. The number of discontinuities longer than 2 mm. is usually less than 30 percent of the total number of all discontinuities and is preferably less -than 15 percent. 'In' general, the minor portion occupies 3 to 20 percent, preferably 4 to 15 percent, of representative cross-sectional areas along the filament and is usually 1 to 3 microns, preferably 1.4 to 2.6 u, in thickness, measured from the abraded surface. The filament is capable of crimping when given a heat-relaxation treatment for 5 minutes in air at 180C. The abraded surface of the filament is generally on the outside of crimp bends and is marked by closely spaced, parallel ripples which extend transversely with respect to the filament length. These ripples are clearly visible when the filament is viewed under high magnification.

A'heatrelaxed product of the invention is as defined above and further characterized by crimp frequency values, measured after a heat-relaxing treatment for 5 minutes in 180C. air and normalized for 2.5 denier per filament, which average at least 10, preferably 25 to 60, crimps per filament inch with a percent coefficient of variation of less than 30, preferably less than 20. Preferablyatleast 95 percent of the filament length has greater than 15 crirnps per filament inch and the crimp frequency distribution for the middle percent is numerically equal to or less than said average (usually from 0.4 to 0.9 times the average crimp frequency value Preferably at least 90 percent of the filament 7 length has greater than crimps per inch.

Crimp frequencies are expressed herein as crimps per filament inch, rather than crimps per straight line inch of crimped length. The measurement is accomplished by extending the filament under a load sufficient to straighten the crimps without stretching the filament, marking l-inch (2.54 cm.) distances along the filament, then removing the load to allow recrimping, and counting the crimps between l-inch (2.54 cm.) marks. in order to compare filaments of different deniers, the measured crimp frequency values are multiplied by V d/2.5, where d is the denier per filament after 180C. treatment, to obtain normalized crimp frequency values. If the percent shrinkage (S) in the 180C. oven-relaxing treatment is known, the value of d can be determined by multiplying the unrelaxed denier per filament by (1 S/lOO).

A characteristic abraded surface, which extends sub stantially continuously along one side of the filaments of this invention, provides a qualitative distinction from prior art filaments that have been modified in different ways to impart crimp. The location of modified filament portions in heat-relaxed filaments is indicated by closely spaced, parallel ripples crossing the filaments. FIG. 3 shows the crimp frequency distributions of products produced as described in Example 1 below and then heat-relaxed for 5 minutes in 180C. air. The nor malized crimp frequency in crimps per filament inch is indicated on the abscissa, and the percent of the fila-. ment length having greater crimp frequencies is indicated on the ordinate. The distribution curves are numbered to correspond to yarn numbers. The graph can be used to ascertain the percent of the filament length which has a crimp frequency greater than any given value. The average crimp frequency is the value where the 50 percent ordinate value intersects the curve. The crimp frequency distribution for the middle 90 percent is the minimum crimp frequency for 5 minus the minimum crimp frequency for 95 percent; which will be abbreviated R R Woven and knit fabrics containing relaxed yarns of this invention have desirable bulk aesthetics, performance and uniformity. For example, yarns of the type described in Example [-3 below, when relaxed in a hot air jet and then woven into fabrics, yield fabrics that have a high degree of suppleness and liveliness; warpknits from similarly relaxed yarns have a soft hand, high bulk, and excellent dye-uniformity. Double-knit fabrics prepared from relaxed yarns of Example I, yarn sample 2, have a high, firm bulk and excellent wash-wear performance, wrinkle-resistance, and dye-uniformity. Suitable filaments for such yarns are between 1 and 7 denier per filament. The yarns of the present invention can also be cut into staple lengths and converted to yarns or used as filling, as in pillows, after developing the crimp.

EVALUATION PROCEDURES Photomicrographs of Filament Surfaces A scanning electron microscope is used to examine the nature of the abraded surface of the filaments. A short sample (about 1.9 cm. long) of yarn is mounted on a standard Stereoscan stub (1.9 cm. diameter aluminum stub). Two strips (0.32-cm cm. X 0.63-cm.) of double-faced adhesive tape are fixed l.27-cm. apart and parallel to each other on the stub surface. The sample of yarn is lightly teased to separate thefilaments and each yarn end is fixed to one strip of the adhesive. When mounting crimped yarn, no tension is applied so that the yarn is mounted with its crimp undisturbed Silver circuit paint is dabbed on both ends of all filaments and on the adhesive tape to insure electrical continuity to the specimen stub. The final step of specimen preparation involves the vacuum evaporation of a 60/40 Au/Pd coating onto the surface of the sample and stub which insures electrical continuity over the entire stub. The thickness of this coating is estimated to be of the order of 300-400 A which is below the level of resolution of the scanning electron microscope used; thus, the coating is not seen when viewing filaments by this technique.

The stub is placed in the specimen holder and after evacuation of the specimen chamber, the specimen is viewed in the scanning electron microscope. Typical viewing conditions are 20 KV electrons with a beam current of 200 ;.:.amps, and a specimen tilt of 30 relative to the impinging electron beam. After areas of the filaments exhibiting modified surfaces are located, micrographs are recorded at, e.g., 200, 500, 1,000 and 2,000X magnifications. This series of magnifications includes a sufficiently low magnification to illustrate the position of the modified surface relative to the crimp and a sufficiently high magnification to reveal details of the modified surface.

When viewed by this technique, unrelaxed filaments of the present invention exhibit a frictionally modified surface running along the filament length; in the relaxed filaments, this surface can be seen to be present along the outside of the crimp bend and can also be seen to have a plurality of ripples. These ripples are visible on the abraded surface and run transverse to the filament length. In the relaxed filaments that have been jet-screen treated (e.g., as in Example 11 below), the modified surface also runs generally on the outside of crimp bends, but may occasionally be seen on the inside where secondary folds have been imposed on sections of the filament by jet-screen impact.

Continuity of the Modified Portion Interference microscopy is used to determine the continuity of the modified portion along filament length Z, where Z is taken as 40 mm. times the number of filaments in the yarn for any yarn having 34 filaments. For other yarn counts, a total of 1,360 mm., distributed uniformly across the yarn, is viewed.

When working with a 34-filament yarn, a 60 mm. length is cut from the yarn. The individual filaments are separated. Each 60-mm. long filament is taped on a glass slide so that it lies straight. The slide is immersed in Refractive Index Fluid of an index of refraction (n) which matches the index of refraction (n perpendicular) of the unmodified portion of the filament for light vibrating perpendicular to the fiber axis (e.g., a fluid of n 1.540 is used for polyethylene terephthalate). The filament, after immersion in the fluid, is then covered with a second glass slide and the assembly is placed on the stage of the interference microscope. The assembly is advanced across the viewing area so that a continuous 40 mm.-length is viewed at 200X.

The presence of a modified portion is detected by interference contrast (i.e., the modified portion will be of different color than the remainder of the filament) or by fringe field (i.e., a fringe shift indicates a change in index of refraction going from modified to unmodified areas of the filament). Only those sections where a The following are determined:

number of divisions M total number of all discontinuities N number of discontinuities greater than 2 mm. (2

mm. 400 divisions) U sum of the lengths of all discontinuities, expressed in mm.

W sum of the lengths of discontinuities greater than 2 mm., expressed in mm.

Z total filament length viewed From these values, the following are calculated:

Average length of all discontinuities U/M of long 2 mm.) discontinuities (N/M) X 100 of filament length occupied by long 2 mm.) discontinuities (W/Z) X 100 The products of the present invention have a low average length for all discontinuities, and the long discontinuities, if present, occupy only a very minor portion of the total legnth of the filament. It is believed that these factors contribute significantly to the desirable crimp of the products, since the presence of the modified portion correlates well with the development of crimp in the filaments.

Dimensions of Modified Portion: Cross-Sectional Views A cross-section of the yarn sample is suitably prepared for microtome sectioning, e.g., a yarn bundle is mounted in a Beem capsule and embedded with epoxy (Maraset from Marblette Corp.). After trimming the cured stub, approximately 6 micron thick sections are obtained using a rotary microtome (Spencer Model 860) with a steel blade. The sections are placed onto the two halves of a cut microscope slide (insures constant thickness for a two beam Leitz Transmission Interference Microscope). The two specimen slides are completed by immersing the sections in refractive index oil (Cargille Index of Refraction Fluid N 1.530) and covering iwth microscope cover slips.

One specimen slide is placed onto the reference beam stage and the other slide is placed onto the sample beam stage of the two beam Leitz Transmission Interference Microscope. The specimen section is viewed at 500 magnification. Following the alignment procedures, thefringe field is obtained in the field of view in white light. The fringes are then fluffed out to obtain interference contrast, i.e., the fringes are taken to their maximum separation. The specimen section is brought into sharp focus and the index variation across the textured filament cross-section is recorded on color film as the retardation or color difference across the filament section. The procedure can be carried out in monochromatic illumination and recorded on black and white film. The procedure described above is performed without the analyzer in the optical system and is used as a qualitative detection technique for presence of the modified portion of different refractive index.

Thickness of the modified portion is determined from l,OO0 micrographs of cross-sections by measuring with a ruler the thickness on three cross-sections at three points each, and averaging the nine values. In these measurements 1 mm. l u. The three points measured on the photomicrograph are (l) the thickness at the center of the modified portion and (2) and (3) the thickness near each of the extremes of the modified portion, measured at a distance of about 1 mm. from each extreme.

The width of the modified portion at its widest point and the diameter of the filament are also measured on l,OO0 micrographs of cross-sections. Four or five cross-sections per sample are analyzed and the average of the four or five determinations is recorded.

The area of the modified portion is determined by making a l,OO0 photomicrograph, cutting out 8-12 cross-sections from it, and weighing these cross-sections before (W and after (W cutting the modified portion therefrom. Area= (W,; (lOO/ W when W and W are total weights in grams, before and after cutting.

Crimp Frequency Distribution For a yarn having at least 17 filaments, a 50-cm. length of yarn is cut from the yarn to be tested, and 17 filaments, taken at random, are carefully separated from the cut length, taking care not to stretch the filaments. One filament at a time is relaxed as follows: The filament is suspended by attaching both ends to a glass rod at a sufficient distance apart to permit the filament to shrink and crimp fully without becoming taut; this is done, e.g., by attaching masking tape or a suitable clip to each end of the filament and clipping each end to the rod. The rod may be permanently mounted in the oven or placed in the oven, with the filament already attached to it. Hot air at C. is gently circulated in the oven for 5 minutes by the oven blower, which is set at minimum to avoid filament entanglement. A suitable oven for this test is Electric Hotpack Co., Inc., Model 1354. The thusly suspended filament is free to relax. Then, taking care not to stretch the filament, the filament is removed from the oven and is carefully placed in a relaxed condition on a velvet board. After removal of each specimen, the oven is allowed to come back to 180C. (e.g., 5 minutes) before the next specimen is placed in the oven. This is repeated until all 17 filaments have been relaxed, individually.

One end of each relaxed filament is then taped to one end of a clear plastic straight-edge which is marked in l-inch (2.54 cm.) intervals. A weight, sufficient to straighten the crimps without stretching the filament, is taped to the free end of the filament. For example, a 0.6 g. weight is normally satisfactory for filaments of about 2 to 6 dpf. The straight-edge is lifted to a vertical position, allowing the filament to hang freely under the tensioning weight. The filament is then taped to the straight-edge near the weighted end, while under tension. With a black felt-tipped marking pen, twelve consecutive l-inch sections are marked off on the filament. The filament is then removed and taped at its ends, re-

laxed, on a second, clear straight-edge. The markings on the filament are duplicated on the second straightedge along side of the filament with a black felt pen. This allows direct measurement of the crimps per filament inch. The number of crimps between the markings are counted at about 20 X magnification using a shadowgraph (e.g., Nippon Kogaku K.K., Japan, Model 6). Crimps per each filament inch (cpi) for a total of 204 one-inch filament sections per sample are recorded (17 filamentsX l2 one-inch sections).

1f the yarn contains less than 17 filaments total, a sufficient length of yarn is used, so that the number of filaments times the length equals 204 inches (5l8-cm.).

The number of one-inch sections in each of a series of crimp ranges (-5 cpi, 6-10 cpi, 1 1-15 cpi, etc., in increments of cpi/range) is counted and the percent of filament length within a given crimp range is calculated by:

Number of l-inch sections in given crimp range X 100 204 sections Data are reported in terms of filament length present, having a crimp frequency greater than a given level, using as levels the upper limit of each crimp frequency range, i.e., 5 cpi, 10 cpi, cpi, etc. The respective observed crimp frequency values are multiplied by V d/2.5 to obtain normalized crimp frequency values, where d is the denier per filament after the heatrelaxing treatment in 180C. air for 5 minutes. Any accurate method can be used for determining 1. The method used herein is to multiply the denier per filament before the heat-relaxing treatment by (l 1 S/lOO), where S is the percent shrinkage calculated from yarn lengths before and after the heat-relaxing treatment when measured under sufficient tension to just straighten any crimps without stretching the yarn (a tension of grams is suitable for 34-fi1ament yarns in the Examples unless otherwise specified).

Illustrative data for one of the examples (i.e., Ex. 1, yarn 2) is given below: I

Crimp Range at No. of l-inch /r Filament d dpf (cpi) Sections Length Present The above data may be expressed as follows:

-continued Crimp Level Crimp Level at d dpf (Normalized for 2.5 dpf) 0% 50 cpi cpi The above determined data are plotted on a graph as filament length with crimp frequency greater than vs. crimp frequency level, normalized for 2.5 dpf. This graph can then be used to ascertain filament length with crimp frequency greater than any given value of crimp frequency.

The crimp frequency distribution for the middle percent is defined as R5"R95, where R is the value read from the graph at the 5 percent level and R is the value read at the 95 percent level. For a narrow crimp frequency distribution, the ratio of R R to the average crimp frequency is equal to or less than 1.

The percent coefficient of variation is defined as the standard deviation of the individual determinations of crimp frequency (F), times and divided by the average crimp frequency in crimps per inch. The standard deviation is calculated by the formula:

Standard deviation where N is the number of determinations. A percent coefficient of variation which is less than 30 indicates a narrow crimp frequency distribution and a value less than 20 indicates a highly uniform crimp.

1n the Examples unless otherwise specified, a yarn finish is applied by conventional means (i.e., lst and 2nd finish-applying rolls referred to in the discussion of FIG. 1). This finish, referred to hereinafter as finish A, is a 3.9 percent aqueous mixture containing 49 parts of isocetyl stearate, 24.5 parts of sodium di-(2- ethyl-hexyl)sulfosuccinate, 24.5 parts of the condensation product of 1 mol of stearyl alcohol with 3 mols of ethylene oxide, 1 part of triethanolamine and 1 part of oleic acid. The total amount of finish applied to the filaments is approximately 0.3 i 0.1 weight percent finish on yarn after drying, based on the weight of yarn.

Just before wind-up, (e.g., at roll 19' of FIG. 1) the yarn is treated with another conventional finish (noted hereinafter as finish B) which is an aqueous mixture containing 20.5 parts of sulfated peanut oil, 1.8 parts of diethylene glycol, 1.8 parts of KOH, 62.6 parts of the ester formed from l-butanol and a 45-55 mixture of stearic and palmitic acids, 8.2 parts of oleic acid, 3.4 parts of triethanolamine, and 1.7 parts of ortho phenylphenol. This second finish is applied to give a total of A plus B of about 0.5 i 0.15 percent finish on the yarn after drying.

1n the Examples, the process of the invention is illustrated with yarns having filaments of circular cross-section, although the process may operate satisfactorily with yarns of other cross-sections as well. Break elongation and boil-off shrinkage are measured on filaments before or after pin-texturing: break elongation by ASTM-D-2256-69; and boil-off shrinkage by comparing filament length before and after 30 minutes exposure in boiling water. Unless otherwise specified, yarn tension is measured with a Schmidt-Waldkraiburg tensiometer (O-lOOO gram scale).

13 Different texturing pins are used in the examples. These are identified as follows:

Some typical thermal conductivities and coefficients of friction (measured by the technique described by J. S. Olsen, Frictional Behavior of'Textile Yarns, Textile Research Journal, Vol. 39, No. 1, Jan., 1969, using a 6-gram input tension and a 500-yd./min. [457 me ters/min.] speed) for these pins are:

Thermal Conductivity Coefficient Type (cal./cm.sec.C.) of friction la 0.124 10* 0.48 3 0.41 X 10 0.56 4 0.124 0.82

Alsimag is a registered trademark in the US. for pressed and extruded steatite thread guides, beryllia ceramics, and leachable ceramic cores. Steatite is a mixture of clay, talc and alkaline earth oxides. The Alsimag pins used in the Examples are made by American Lava Corp. of Chattanooga, Tenn. Pins having friction coefficients of 0.2-1.2 are suitable for use in the invention; coefficients of 0.4-0.8 are preferred.

EXAMPLE I This Example illustrates the production of six polyester yarns in accordance with the present invention. Process conditions are summarized in Table I. The crimp characteristics of the resultant yarns are presented in Table I1. Crimp frequency distributions for the first five yarns are plotted in FIG. 3.

All of the yarns of this example, except yarn 5 are prepared by a continuous process in which polyethylene terephthalate polymer is melt-spun, drawn and pintextured as shown in FIG. 1. The process for yarn 5, illustrated in FIG. 2, involves the use of previously meltspun, drawn and packaged commercial semi-dull polyethylene terephthalate filaments. These yam-5 fila' ments, prior to pin texturing, formed a 34-filament, 70 denier yarn having a boil-off shrinkage of about percent and a break elongation of about 36 percent Finishes A and B were applied to yarn 5 prior to pin texturing, as described above. In the pin texturing of yarn 5, per FIG. 2, an inner wrap of yarn, lifted from the stretch rolls 25, passes over the texturing pin 26 and back around the stretch rolls before the yarn continues to the wind-up 28. Yarns 3 & 4 illustrate the use of very short contact lengths on the texturing pin. Yam 6 illustrates the use of relatively low viscosity filaments. All polyester relative viscosities listed in Table'l and subsequent tables are measured at C. in a solution of 8 grams of polymer in 100ml. of hexafluoroisopropanol containing 100 parts per million of sulfuric acid-.:=

In the drawing steps for yarns 1 through 4 and. 6, the draw rolls are located in a temperature-controlled en- 14 closure, called a draw box. Since the filaments in this example lose very little heat in traveling from the draw box to the texturing pin, the yarn temperature at the feed pin is listed in Table I as being at the same temperature as the draw box.

Yarn 2, which as indicated in Table l, is produced in a similar manner to yarn 1, but is further processed by ajet-screen-bulking step. After pin-texturing, the yarn is fed at about 3000 yards/minute (2740 meters/minute) at a temperature of about 125C. to a hot-air jet device which deposits the yarn on a screen drum as i1- lustrated in Clendening US. Pat. No. 3,217,386. The jet device is of the type disclosed in Coon US. Pat. No. 3,525,134 and is supplied with hot air at 335C. and pounds per square inch (7kg/cm gauge pressure. The jet device comprises a longitudinal yarn passage terminating in a short length having a width d,- of 0.033- inch (0.085 cm.) and a depth of 0.030-inch (0.076 cm.); a throat region having a width d, of 0.045-inch (0.114 cm.); an expanding treatment chamber whose sides diverge at an angle B of 45 from the throat region to a width d of 0.22-inch (0.56 cm.) at the chamber exit; and dual fluid conduits, each having a width d, of 0.025-inch (0.064 cm.), disposed on either side of the yarn passage and intersecting the throat region at an angle a of 30. The dual fluid conduits and the yarn treatment chamber have the same depth of 0.060-inch (0.1-52' cm.)

The heated air supplied to the jet device forwards the yarn through the treatment chamber, plasticizes it and propels it against a screen surface on a rotating relaxing drum. The screen drum surface is of 40-mesh, located 0.050-inch (0.127 cm.) from the jet exit and revolving at 700 feet per minute (213 meters/minute). Residence time on the drum is 0.12 second. The treated yarn is taken from the screen drum at about 2,220 yards per minute'(2,0l0 "meters/minute) by a pair of rolls and proceeds at 20 grams tension to a wind-up for packaging. Table 11 lists the properties and FIG. 3 shows the crimp frequency distribution of the final product (i.e., the pin-textured product that has also been jet screen bulked).

EXAMPLE II This example describes another embodiment'of the invention in which polyester filaments which have been melt-spun at relatively high speeds are pin-textured and then jet-screen bulked. Process conditions for the drawing and pin-texturing steps are given below and in Table l; The crimp characteristics of the final product are summarized in Table II.

Polyethylene terephthalate of 19.5 relative viscosity and containing about 0.3 percent, by weight, of TiO delusterant is melt-spun at 284C. through a spinneret having 34 round holes, each hole having a diameter of 0.01 l-inch (0.028 cm.) and a length of 0.020-inch (0.051 cm.). The freshly spun filaments are quenched with air at 23C. in crossflow against the filaments and then passed through a guide, past a finish roll to a pair of puller rolls, situated 188 inches (4.78 meters) below the spinneret and revolving at a peripheral speed of 3,398 ypm (3,107 meters/minute). The yarn wraps around these rolls and, subsequently, passes around rolls moving at 3,403, 3,409, and 3,413 ypm, (3,112, 3,117, and 3,121 meters/minutes) respectively, which maintain tension on the yarn. The yarn then passes through an interlace jet and to a second finish roll and is then wound up at 3,41 1 yards per minute (3,1 19 meters/minute) to form a package.

The interlace jet is of the type described in Bunting et al. US. Pat. No. 3,1 15,691. The interlace jet produces an interlace pin count, as measured according to Hitt US. Pat. No. 3,290,932, of about cm.

Finish is applied at first and second finish rolls in an amount of 0.50 percent, based on the weight of the fiber. The finish is of the general type described in U.S. Pat. No. 3,594,200 to Cooley and Finch. lts composition is as follows: 28 parts of coconut glycerides, 37 parts (on a wet basis) of sulfated peanut glycerides having a 20 percent water content, parts of Gafac PE- 510, i.e., an acid phosphate of ethoxylated nonylphenol as depicted by the formula at Col. 2, line 5 of U.S. Pat. No. 3,594,200, and 10 parts of Shell 277 (a mixture of paraffinic and alicyclic hydrocarbons). To this mixture is added enough 45% KOH to give a pH of 6.5.

The yarn obtained in this fashion is a 247 denier-34- filament yarn having a tensile strength of 2.47 grams per denier, an elongation of 129.1 percent, and an initial modulus of 30.94 grams per denier. An X-ray pattern of the yarn shows that it is amorphous, having no measurable crystallinity. The orientation angle is 14 and the density of the filaments is 1.342 grams per cc.

The as-spun yarn from its package is then led to a pair of feed rolls rotating at a peripheral speed of 668 yards per minute (61 l meters/min.) making 7-8 wraps about the rolls then passed in sliding contact with ice cold metal finish roll rotating in an ice/water bath. From the finish roll the cooled yarn travels a distance of less than about 8 inches to a T-pipe having a yarn passageway with a diameter of Aa-inch (1.59 cm.) and length of 10 inches (25.4 cm.) into which atmospheric steam is fed. As the yarn passes through the pipe, it is subjected to the 95-100C. mixture of hot water and atmospheric steam in the pipe. Steam exits from the pipe at the entrance and exit of the yarn passageway. From the pipe, the yarn passes a distance of less than about 8 inches (20.3 cm.) to a second ice cold metal finish roll rotating in bath containing a mixture of ice and water. The cooled yarn then passes to a pair of draw rolls rotating at a peripheral speed of 1,499 yards per minute, (1371 meters/min.) making 8-9 wraps about the rolls. in its passage from the feed rolls to the draw rolls, the yarn is drawn 1.94X. The drawn yarn has an elongation of about 13-14 percent. The yarn then passes from the draw rolls over a Type 3 unheated AlSi- Mag 192 texturing pin. The AlSiMag pin is stationary and the yarn passes over it in frictional contact with it an an angle of 90". From the pin the yarn passes to rolls rotating at a speed of 1,518 yards per minute (1,388 meters/min.) making 5-6 wraps about the rolls and then to a package.

Tension on the yarn during drawing, as measured with a Schmidt-Waldkraiburg tension measuring device inserted in the running line, is 190 grams. Yarn tension measured in the same way before and after the pin is 50-90 grams (before) 200-230 grams (after). The calculated AT max parameter for this process is 273C.

The properties determined on the pin-treated yarn are as follows:

Density (grams per cc): 1.364 Denier: 130 Tenacity (gpd): 4.42 Elongation (70): 13.6 Modulus (grams per denier) 98.14 Yield Tenacity (grams per denier) 1.35

-continued Crystallinity Index: Orientation Angle:

The yarn is then unwound from a package and subjected to a jet/screen relaxing treatment under the following conditions: The yarn is led to a set of feed rolls rotating at a peripheral speed of 1,455 yards per minute, (1,330 meters/min.) making 12 wraps about the feed rolls. From the feed rolls the yarn passes into a jet.

The jet device used is of the type described in Yngve US. Pat. No. 3,638,291. Referring to FIG. 2 of the Yngve patent, the dimensions of the jet are as follows:

The jet is supplied with steam at 25 to 28 psi (1.76 to 1.97 kg/cm gauge and 300 to 305C. From the jet the yarn is impacted against a screen mounted on drum moving at a peripheral speed of 7 yards per minute (6.4 meters/min), the drum being a 3 /z-inches (8.9-cm.) wide, 15-inch (38.1-cm.) diameter drum having a mesh screen on its surface. An accumulated mass of yarn travels for a distance of about 15 inches (38.1 cm.) along the drum circumference. From the drum the yarn passes over guide rolls to a wind-up where it is wound up at about 1,100 yards per minute (1,006 meters/min) The untwisted yarn has the following properties:

Additional properties are given in Table 11.

A sample of the yarn is then knit into a Swiss-pique fabric (18-cut). The fabric has good bulk and desirable hand, texture and appearance.

EXAMPLE 111 This example illustrates pin-texturing of polyester filaments in five continuous high speed process embodiments of the invention, in which several process parameters were varied; for example, pin composition, texturing speed from 1,300 to 2,800 yards/minute (1,189 to 2,560 meters/min.) and pin contact length. This series of runs, along with those of the other examples and numerous other data, were useful in developing the AT max parameter for defining preferred operating conditions of the invention.

In each of runs A through E, polyethylene terephthalate polymer of 22.0 relative viscosity and containing turing step are summarized in Table III. The tensions 5 are measured with a Rothchild Tensiometer having rolling guides with high speed bearings on the tension head, using the to IOOO-gram tension range. The apparatus arrangement of FIG. 1 is used. Characteristics of the pin-textured yarns are given in Table IV.

EXAMPLE IV This example illustrates the process of the invention with two types of multifilament polyamide yarns. Yarn A is Zytel 101, made'from polyhexamethylene adipamide (6-6 nylon) of 45 relative viscosity. Yarn B is made from the polyamide, called PACM-l2, which is obtained from bis-(para-aminocyclohexyl)methane and dodecane dioic acid. The filaments are pin textured on unheated glass rods (Type Each polyamide yarn is spun, drawn and wound up Yarn A Yarn B 6-6 Nylon PACM-l2 Tenacity(gpd.) 5.6 3.5 Elongation( 7:) 22 24 Modulus(gpd.) 3 1 35 Denier 130 227 Density 1.1295 1.0802 Orientation Angle() 16 32 Crystallinity Index 48 5 In a separate step, each yarn is passed over two sets of rolls and then the fully-drawn yarn is passed over a glass pin to a third set of rolls. Passage over the glass pin frictionally modifies the yarn and imparts latent crimp. Process conditions are given in Table III and properties of the pin-textured filaments are given in Table IV The resultant crimp, while less than that obtained in Examples 1, II and III with pin-textured polyester yarns, is sufficient to impart increased bulk to the polyamide yarn, which in turn improves tactile properties of fabrics such as tricot for slips, blouses and the before being pin textured. Properties of typical yarns like Table l Pin-Texturing of Polyester Filaments of Examples 1 and 11* Example No. l l l l I I 11 Sample No. 1 2 3 4 5 6 Polymer relative viscosity 22.0 22.0 20.3 20.3 (c) 15.0 19.5 Drawing Step Feed roll speed, meters/min. 638 638 638 638 (d) 559 611 Jet temperature, C 225 225 210 185 (cl) 225 100 Jet pressure, psig(kg/cm. 85(6) 85(6) 98(6.9) 60(4.2) (d) 85(6) 14.7(1) Draw roll speed, meters/min. 2560 2560 2533 2533 887(e) 2561 1371 Draw ratio 4.0 4.0 4.0 4.0 (d) 4.6 1.94 Pin-texturing step Yarn temperature, C(a) 42 105 RT. 76 R.T. 70 -0 YP W) Tension before pin, g./fil. 5.1 3.4 (c) (c) 3.1 1.8 2.1 Tension after pin, g./fil. 7.2 5.1 (c) (c) 5.4 4.1 6.4 Tension change, g./fil. 2.1 1.7 (c) (c) 2.3 2.3 4.3 Contact length, cm. 0.5 0.5 0.12 0.12 0.36 0.75 0.75 Average velocity, cm./sec. 4308 4371 4182 4290 1554 4346 2299 A T max. parameter, "C 216 172 (c) (c) 233 209 273 Pulling roll speed, meter/min. 2612 2686 2487 2615 978 2654 1388 stretch between draw & pull rolls 2 5 0 3 10 3.6 1 Windup speed 2567 2628 (c) (c) 956 2612 1388 Pin-textured yarn Denier 144 141 71 72 70 127 130 Number of filaments 34 34 34 34 34 34 34 Break elongation, %(f) 38.1 34.5 31 36 28.4 -13.5 Boil-off shrinkage, %(f) 16.8 9.8 16.7 16.4 10 11.5 -17 Break elongation, %(g) 30.6 28.4 32 30 (c) 24 13.6 Boil-off shrinkage. 7z(g) 17.7 11.3 18.3 16.3 (c) 11 17 Notes:

(a)R.T. room temperature. (b)Pin types identified in text. (c)These parameters were not measured or calculatedv (d)Commercial yam with fully drawn filaments is fed; drawing step is by-passed. (e)Speed as removed from package. (f)Filament properties before pin-texturing. (g)Filament properties after pin-texturing.

before pin-texturing are as follows:

Table II Pin-Textured Filaments of Examples 1 and 11 A. Modified Portion of Filament l-l -Z I3 [-4 l-5 [-6 ll Thickness, microns 2.3 2.1 1.6 1.4 1.4 1.9 1.5 Width of filament diameter 35 53 49 45 46.2 54.8 Area occupied, of fil. cross-section 4.9 5.9 8.4 7.6 7.9 5 5.7 Average length of discontinuities, mm. 0.97 1.04 2.08 0.68 1.25 1.01 1.39 Discontinuities longer than 2 mm.:

7: of total number 0 0 25 0 7 0 of filament length 0 0 2 0 l 0 3.4 B. Crimp Characteristics Average crimps per 2.54 cm. V 43 55 41 39 34 34 49 of fil. length with more than:

15 crimps/2.54 cm. 99 100 100 99 100 100 100 20 crimps/2.54 cm. 7 98 100 100 98 100 100 100 Distribution of middle R -R 40 25 33 27 21 15 19 (R R v ra 0.92 0.4 0.8 0.69 0.62 0.44 0.39

Table ll-continued Pin-Textured Filaments of Examples 1 and 11 A. Modified Portion of Filament" l-1 l-2 [-3 l-4 l-S l-6 ll Coefficient of variation. 27.1 13.1 22.8

Notes:

"Mcasured before the heat relaxation treatment.

"Measured after relaxation for min. in air at 180C.

l-2 and 11 are samples that were also jet-screen bulked.

Crimp is given in crimps per 2.54 cm. of filament length.

All crimp characteristics are normalized to 2.5 denier/filament.

Table III Pin-Texturing of Filaments of Examples 111 and 1V* Example No. lll-A lllB lll-C lll-D lll-E lV-A lV-B Polymer 2GT 2GT 2GT 2GT 2GT Nylon PAC M- 1 2 Polymer. relative viscosity 22.0 22.0 22.0 22.0 22.0 40

Drawing Step Feed roll speed. meters/min. 415 415 623 623 265 860 529 Jet temperature. "C. 225 225 225 225 225 Jet pressure. psig(kglcm. (6) 85(6) 85(6) 85(6) 85(6) Draw roll speed. metcrs/min" 1875 1875 2560 2560 1 189 1 189 1 189 Draw ratio 4.5 4.5 4.1 4.1 4.5 4 2.3 Pin-Texturing Step Yarn temperature. "C. 9O 92 92 60 R.T. R.T. Pin yr Tension before pin. g/fil. 2.5 3.2 2.5 0.9 2.5 0.3 4.4 Tension after pin. gtlfil. 4.2 4.3 4.1 2.9 4.4 4.7 9.4 Tension change. g./fil. 1.7 1.1 1.6 2.0 1.9 4.4 5.0 Contact length. cm. 0.37 0.25 0.37 0.75 0.50 0.50 0.50 Average velocity, cm./sec. 3179 3179 4374 4310 2001 1981 1974 A T Max. parameter. C. 183 .207 184 141 272 219 Pulling roll speed. meters/min. 1939 1939 2688 2612 1212 l 189 1 7! stretch between draw & pull rolls 3.4 3.4 5 2 2 O -().8

Windup speed. meters/min. 1903 1903 2633 2560 l 179 1 189 1 180 Pin textured yarn:

Denier 123 123 123 124.5 127.5 131 258 Number of filaments 34 34 34 34 34 34 34 Break elongation. 92" 30.2 28.6 29.4 32.2 34.2 m

Boil-off shrinkage. 71"" 12.7 11.8 13 12.1 14.1

Break elongation. 7("" 24.9 24.1 28.0 31.5 24.9 22

Boil-off shrinkage. 70"" 11.3 11.6 12.0 11.0 10.3 10 7 *Notes:

""R.T.=room temperature.

""Pin type identified in text.

"l'hese parameters were not measured.

"Not used for polyamide filaments.

""The nylon feed yarn of lVA was previously lully drawn and had a 1.4X recoverable stretch. "Measured in a solution of 0.5 g. of polymer in 100 c.c. of Fomal for Ex. lV-A and lV-B. "Filament properties before pin-texturing.

""Filament pro erties after pin-texturing.

Table IV Pin-Textured Filaments of Examples 111 and 1V* lll-A lll-B Ill-C lll-D lll-E l\ /;A lV-B A.Modified Portion of Filament"" Thickness. microns 2.9 2.1 1.8 1. 1.6 Width, of filament diameter 46.3 48.7 43.5 41.0 34.2 Area occupied. 9': of fil.cross section 7.5 5.6 5.1 4.7 3.3 Average length of discontinuities. mm. 0.87 0.58 0.84 0.73 0.72 1.1 Discontinuities longer than 2mm.:

7c of total number 0 O 0 0 0 5 of filament length 0 O 0 O O 0.5 B.Crimp Characteristics Average crimps per 2.54 cm. 34 41 29 27 27 22 14 7c of fil. length with more than:

15 crimps/2.54 cm. 100 99 100 100 97 98 32 2O crimps/2.54 cm. 100 99 99 96 93 76 0 Distribution of middle 90%, R -R., 14 16 15 13 14 9 9 (R -R flaverage 0.41 0.39 0.52 0.48 0.52 0.39 0.64 Coefficient of variation. 7r 11.3 12.0 13.0 13.8 16.2 10.7 16.0

*Notes:

"Mcasured efore the heat relaxation treatment. "Measured after relaxation for 5 min. in air at 180C Crimp is given in crimps per 2.54 cm. ot'filament length. All crimp characteristics are normalized to 2.5 denier/filth ment. "These parameters were not measured or calculated. lhe tests for these parameters were not ap licable.

We claim: when relaxed, wherein a yarn bundle of filaments spun 1. In the process for preparing multifilament yarn of from a single synthetic linear organic thermoplastic filaments which crimp due to asymmetric shrinkage polymer is passed in contact with a heated surface to provide asymmetric shrinkage properties on opposite sides of filaments, the improvement which comprises (a) drawing the filaments to provide the approximate break elongation desired in the product and (b) passing the drawn filaments at high speed in frictional contact with a durable, wear-resistant surface under frictional tension sufficient to generate all of the heat required to provide the desired asymmetric shrinkage properties without otherwise heating the wear-resistant surface:

2. A process as defined in claim 1 wherein the drawn filaments are passed in frictional contact with the durable, wear-resistant surface at a speed of at least 900 yards per minute.

3. A process as defined in claim 2 wherein the filament speed is 1,000 to 4,500 yards per minute.

4. A process as defined in claim 3 wherein the dura ble, wear-resistant surface is provided by a cylindrical pin 3 to 10 millimeters in diameter.

5. A process as defined in claim 4 wherein the filaments contact the pin over an arc of 30 to 180.

6. A process as defined in claim 2 wherein the filament speed is at least 2,000 yards per minute.

7. A process as defined in claim 1 wherein the filaments are drawn to have a boil-off shrinkage of 5 to 25 percent when determined prior to step (b).

8. A process as defined in claim 1 wherein the filaments are drawn to have 15 to 40 percent elongation at break and 8 to 16 percent boil-off shrinkage.

9. A process as defined in claim 1 wherein the drawn filaments are fed from step (a) to step (b) at a temperature of 25 to 100C.

10. A process as defined in claim 1 wherein the tension on the filaments immediately after contact with the wear-resistant surface minus the tension immediately before the surface is 0.7 to 7 grams per filament for filaments of 1.5 to 10 denier.

1 l. A process as defined in claim 10 wherein said tension difference is l to 2 grams per filament and the filaments are composed of a polyester.

12. A process as defined in claim 1 wherein the filaments are in frictional contact with the surface for a distance of 0.5 to millimeters.

13. A process as defined in claim 1 wherein the filaments are in frictional contact with the surface for a distance of l to 10 millimeters.

14. A process as defined in claim 1 wherein the temperature rise calculated by the following formula is 100 to 300C:

22 where f and f are the average tensions on the filaments immediately before and after frictional contact with the wear-resistant surface, in grams per filament; V is the average speed of the filaments contacting the surface, in centimeters per second; L is the frictional contact length between the filaments and the surface, in centimeters; k is the thermal conductivity of the filaments, in cal./cm.sec.C.;d is the specific heat of the filaments, in cal./g.C.; and a is the denier per filament.

15. A process as defined in claim 1 wherein the wearresistant surface is a curved surface.

16. A process as defined in claim 1 wherein the wearresistant surface is the surface of a ceramic pin.

17. A process as defined in claim 1 wherein the filaments are composed of a polyamide.

18. A process as defined in claim 1 which is a coupled spin/draw/pin-texturing process wherein the yarn is drawn to have l5 to 40 percent break elongation and 8 to 16 percent boil-off shrinkage.

19. A process as defined in claim 1 wherein the filaments are composed of polyethylene terephthalate.

20. A process for treating multifilament yarn to impart asymmetric shrinkage properties to drawn yarn filaments of denier per filament (d) and consisting of a single synthetic linear polyester composition, which comprises passing the drawn filaments at a high speed (V) in frictional contact with an unheated ceramic pin for a frictional contact length (L) of 0.05 to 1.5 centimeters under tension conditions which apply a filament stretch of 2 to 5 percent, said pin having a coefficient of friction of 0.2 to 1.2 and said filaments having a temperature of 25 to C. just prior to contact with the pin, the values of said variables'being such that the temperature rise calculated by the following formula is at least C:

where f and f are the average tensions on the filaments immediately before and after frictional contact with the pin.

21. A process for treating the filaments of a multifilament yarn as defined in claim 20, wherein said yarn has been drawn to have an elongation of 15 to 40 percent and a boil-off shrinkage of 8 to 16 percent before the yarn filaments are passed in contact with said pin. 

2. A process as defined in claim 1 wherein the drawn filaments are passed in frictional contact with the durable, wear-resistant surface at a speed of at least 900 yards per minute.
 3. A process as defined in claim 2 wherein the filament speed is 1,000 to 4,500 yards per minute.
 4. A process as defined in claim 3 wherein the durable, wear-resistant surface is provided by a cylindrical pin 3 to 10 millimeters in diameter.
 5. A process as defined in claim 4 wherein the filaments contact the pin over an arc of 30* to 180*.
 6. A process as defined in claim 2 wherein the filament speed is at least 2,000 yards per minute.
 7. A process as defined in claim 1 wherein the filaments are drawn to have a boil-off shrinkage of 5 to 25 percent when determined prior to step (b).
 8. A process as defined in claim 1 wherein the filaments are drawn to have 15 to 40 percent elongation at break and 8 to 16 percent boil-off shrinkage.
 9. A process as defined in claim 1 wherein the drawn filaments are fed from step (a) to step (b) at a temperature of 25* to 100*C.
 10. A process as defined in claim 1 wherein the tension on the filaments immediately after contact with the wear-resistant surface minus the tension immediately before the surface is 0.7 to 7 grams per filament for filaments of 1.5 to 10 denier.
 11. A process as defined in claim 10 wherein said tension difference is 1 to 2 grams per filament and the filaments are composed of a polyester.
 12. A process as defined in claim 1 wherein the filaments are in frictional contact with the surface for a distance of 0.5 to 15 millimeters.
 13. A process as defined in claim 1 wherein the filaments are in frictional contact with the surface for a distance of 1 to 10 millimeters.
 14. A process as defined in claim 1 wherein the temperature rise calculated by the following formula is 100* to 300*C.:
 15. A process as defined in claim 1 wherein the wear-resistant surface is a curved surface.
 16. A process as defined in claim 1 wherein the wear-resistant surface is the surface of a ceramic pin.
 17. A process as defined in claim 1 wherein the filaments are composed of a polyamide.
 18. A process as defined in claim 1 which is a coupled spin/draw/pin-texturing process wherein the yarn is drawn to have 15 to 40 percent break elongation and 8 to 16 percent boil-off shrinkage.
 19. A process as defined in claim 1 wherein the filaments are composed of polyethylene terephthalate.
 20. A process for treating multifilament yarn to impart asymmetric shrinkage properties to drawn yarn filaments of denier per filament (d) and consisting of a single synthetic linear polyester composition, which comprises passing the drawn filaments at a high speed (V) in frictional contact with an unheated ceramic pin for a frictional contact length (L) of 0.05 to 1.5 centimeters under tension conditions which apply a filament stretch of 2 to 5 percent, said pin having a coefficient of friction of 0.2 to 1.2 and said filaments having a temperature of 25* to 100*C. just prior to contact with the pin, the values of said variables being such that the temperature rise calculated by the following formula is at least 140*C.:
 21. A process for treating the filaments of a multifilament yarn as defined in claim 20, wherein said yarn has been drawn to have an elongation of 15 to 40 percent and a boil-off shrinkage of 8 to 16 percent before the yarn filaments are passed in contact with said pin. 